Terminal for edge wound resistors



Aug. 4, 1936. J. F. FRESE 2,050,220

TERMINAL FOR EDGE WOUND RESISTORS Filed June 6, 1935 2 Sheets-Sheet l Aug. 4, 1936. J. F. FRESE TERMINAL FOR EDGE WOUND RESISTORS Filed June 6, 1935 war/144241 Patented Aug. 4, 1936 UNITED STATES A'E'ENT OFFIQE TERIWIINAL FOR EDGE WOUND RESISTORS Application June 6, 1935, Serial No. 25,328

9 Claims.

This invention relates to rheostats and particularly to rheostats of the type in which the resistance elements consist of flat metal ribbons wound on edge and supported on flat supporting members which extend between cross bars in a rheostat frame. The flat metal ribbons are not flexible so that they can be bent easily in any direction like round conductors, and therefore the invention comprises a terminalv block especially designed for easily and securely fastening the edgewound resistors thereto.

One purpose of the present invention is to provide a terminal for each end of each resistance element which is directly applied to the supporting bar for that end of the element and which provides both means for connection to cables and means for interconnection between resistance elements whereby they can be placed either in parallel, in series, or in a combination of these two arrangements and taps can be taken off where desired.

A further feature of the invention resides in the longitudinal spacing of the resistor elements and terminals on the supporting bar whereby frames of resistors may be stacked with the resistance coils either directly above each other or in staggered relationship without affecting the facility with which intercoil connections can be made.

In the accompanying drawings,

Fig. 1 is a top plan view of two banks of resistance elements, one mounted upon the other, with the resistance elements of the two banks in staggered relationship;

Fig. 2 is an end View of the same;

Fig. 3 is a section on the line 3-3 of Fig. 1, showing one of the terminal blocks in central section with the adjacent resistance coil connected thereto;

Fig. 4 is a section on the line 4 of Fig. 3, the clamping cap being also partly in section;

Fig. 5 is a perspective view of one of the terminal blocks with the clamping cap removed, and,

Fig. 6 is a similar view of the clamping cap.

In Figs. 1 and 2 of the drawings, a, b and indicate resistance elementsmounted in a frame 11, and a, b and 0 indicate similar elements mounted in a similar frame (1'. The resistance elements and their supporting frames are substantially like those shown in patent to George H. Whittingham No. 1,687,357. The frames are alike in form and size, each comprising parallel side bars I connected at their ends by cross-bars 2, and supporting brackets 3 consisting of flat metal strips mounted on the cross-bars and having right angled end portions 3 which project outwardly from their central portions and serve as means whereby the banks may be supported as individual units, or connected together as by bolts 4. Each cross-bar is surrounded by a tube 5 of insulating material, as shown in Fig. 4. Each resistance element consists of a flat metal bar 6 having an insulating covering 1 and a helix 8, composed of a flat metal strip or ribbon wound on edge, threaded onto the covering. Each bar 6 has a fork at one end and a hook at the other end, as shown in said patent, so that it can readily be attached to the cross-bars 2 of an assembled frame.

The edgewound coils have not the flexibility of wires and cables, and hence it is desirable to provide special forms of terminal blocks for the coils. The terminal block which forms the subject of the present invention is illustrated in detail in Figs. 3 to 6 and the manner in which these are mounted is illustrated in Figs. 1 and 2. In Fig. 1, terminal blocks 6 for the coils 8 of resistance elements a, b and c are shown at one end of the frame (1, and similar blocks a for the opposite ends of these coils are shown at the opposite end of said frame, the latter blocks being inverted with respect to the former. Similar blocks are mounted on the frame (1' adjacent the ends of the coils on the latter frame.

As shown in Figs. 3 to 6, each terminal block comprises a metal casting having bosses 9 projecting oppositely from its central portion and having a bore l0 extending through these bosses and the body of the block, the diameter of the bore being such that it will fit closely around the insulating tube 5 on a cross-bar 2. At one side of the bore i0 is a part II which projects above the body of the block, the projecting portion of said part being rectangular in cross-section and having beveled faces Il il on the sides which lie parallel with the bore Hi. This part has a bore l2 extending through it, at a right angle to the direction of the bore I0, adapted to receive a clamping bolt I3. At the opposite side of the block from the projection l l, the block is formed with an angular socket !4 open at the top and having a broad outer wall 15 in the central part of which is formed a slot or recess l6 extending downwardly from the top of the wall. The outer face l5 of the socket wall is flat and parallel with the axis of the bore Ii) in the block. The socket is adapted to receive the angular head Mi of a clamping bolt 16* and prevent the bolt 5 from turning, while the shank of the bolt extends through the slot, as shown in Fig. 3, and by a suitable nut and clamping washer on the bolt a fiat metal connecting strip 1, as in Fig. 3, or a cable terminal or, as in Fig. 1, may be clamped against the surface I5 For connecting the end portion 8 of an edge- Wound resistance coil, a clamping cap l l is adapted to fit over the projection M on the terminal block. This cap has a longitudinal slot ill to permit the bolt 53 to pass through, and a transverse slot il to permit the end portion of the resistance coil to pass through, a flange ll of the cap forming one wall of the latter slot. This flange, which is deeper than the other flanges of the cap, has its inner face inclined outwardly and downwardly so as to lie parallel with the beveled face ll of the projection ll when the cap is applied to said projection, as shown in Fig. 3. The opposing flange l'l is similarly inclined on its inner side and fits against the beveled surface ll of the part ll when the cap is in position on said part. To connect the coil 8 to the terminal block, the bolt E3 is inserted in the bolt ill and the cap is then placed upon the projection M, the bolt passing through the slot ll in the cap and the straight end portion 8 of the coil passing through the slot ll A nut l3 applied to the bolt and then tightened causes said end portion to be tightly clamped between the inclined surface of the flange ll and the opposing beveled face ll of the projection ll. The part of the metal ribbon extending above the cap may then be bent outwardly over the cap, as shown in Fig. 3. Thus a good electrical and mechanical connection is made between the coil and the terminal block.

Referring to Figs. 1, 2 and 4, insulating washers 2i! are arranged on the cross-bars at the opposite sides of the fiat metal supporting bar 6 of the resistance units and each terminal block abuts against one of these washers. Insulating Washers M are arranged at the opposite sides of the terminal blocks. The terminal blocks 6, e for the resistance element 1) are at the center of the cross-bars and the terminal blocks for the elements a and c are spaced equal distances from the blocks for the element 2) by spacing tubes 22. The same is true of the mounting of the terminal blocks e on the lower frame d, so that the blocks on the two frames are opposite one another although the resistance coils on the upper frame (1 are at the left of their terminal blocks, While the coils on the lower frame d are at the right of their respective terminal blocks. If it is not desired to stagger the coils, one of the frames may be turned through an angle of to bring the coils on one frame opposite those on the other and the blocks on one frame will still be directly opposite the blocks on the other frame, which makes it possible to use the same connecting strips for connecting the terminal blocks on the two frames in either of the relative positions of the frames.

As the coils of the resistance elements a, b and c are at the left of the terminal blocks and wound counterclockwise, the terminal blocks e are arranged with the clamping caps uppermost so that the upwardly turned extensions 8 of the end convolutions of said coils may be passed through the slots in the caps and clamped as shown in Fig. 3; but the blocks e are inverted with respect to the blocks e in order that the downwardly extending ends 81) of the end convolutions may be passed through the slots in the caps and clamped.

The coils on the two frames may be connected in various ways by the connecting strips which engage the flat faces l5 of the terminal blocks. For illustration, the coils are connected in series as follows: a strip connects one end of coil of element a to one end of coil of element a and the opposite end is connected to coil of element b by strip f; strip f connects coil of element 1) with coil of element b; strip f connects coil of element 1) with coil of element 0, and strip f connects the latter coil with coil of element 0'. Any desired number of banks of resistors may be connected together and cable terminals, such as g, Fig. 1, can be connected to any of the terminal blocks. The terminal blocks 6 on the lower frame of need not be described since they are the same as the blocks on the upper frame.

What I claim is:

l. A terminal member for an edge wound helical resistance coil comprising a unitary casting including a central portion having a hole to fit over a mounting rod extending at right angles to the axis of the coil, a portion at one side of the central portion having a tapered end whose axis extends at right angles to the axes of the hole and coil, a cap to fit over said tapered end and having a corresponding internal taper, a bolt passing through the tapered portion and cap to draw them together, and a slot through the cap to receive one end of the coil.

2. In a rheostat, in combination, a supporting rod, a coil supporting member extending at right angles to said rod and having one end supported thereon, an edge wound resistance coil mounted on said member and extending near to said rod, a terminal block having a hole fitting over said rod, means insulating the member and block from the rod and each other, a projection on the coil side of said block having a beveled face, a clamp thereon to directly receive a tangential end of said coil and clamp it to said face, a projection on the opposite side of said block, and a bolt receiving socket in said last mentioned projection to receive a conductor securing bolt.

3. In a rheostat, in combination, a supporting rod, a coil supporting member extending at right angles to said rod and having one end supported thereon, an edge Wound resistance coil mounted on said member and extending near to said rod, a terminal block having a hole fitting over said rod, means insulating the member and block from the rod and each other, a projection on the coil side of said block extending at right angles to the axis of the coil supporting member and rod, said projection positioned to have a tangential end of said coil pass along one side face thereof, a cap fitting over said projection and having a wedging surface for cooperation therewith, and means to draw said cap over said projection to clamp said end therebetween.

4. In a rheostat, in combination, a plurality of superimposed rectangular frames each having spaced rods supporting between them a plurality of supporting members, an edge Wound resistance coil on each member, said members being uniformly spaced apart but at such unequal distances from the two sides of their frame that upon reversal of a frame its coils will be in staggered relation to the coils of an adjacent frame, each rod having thereon a terminal block for the corresponding end of each coil of its frame, the blocks of each frame being all on the same sides of their coil supporting members and in such relation to each other and the sides of the frame that they are in overlying relation in either positioning of adjacent frames, and means on each block to receive the end of a coil conductor and fastening means of intercoil connectors.

5. In a rheostat, in combination, a plurality of superimposed rectangular frames each having spaced rods supporting between them a plurality of supporting members, an edge wound resistance coil on each member, said members being uniformly spaced apart but at such unequal distances from the two sides of their frame that upon reversal of a frame its coils will be in staggered relation to the coils of an adjacent frame, each rod having thereon a terminal block for the corresponding end of each coil of its frame, the blocks of each frame being all on the same sides of their coil supporting members and in such relation to each other and the sides of the frame that they are in overlying relation in either positioning of adjacent frames, means on each block to receive the end of a coil conductor and fastening means of intercoil connectors, and said intercoil connector fastening means on all blocks of a group of frames being equally spaced in two directions whereby a single type intercoil connector is sufi'icient for all connections.

6. A terminal block for the coil of an edge wound resistor comprising a metal body having oppositely extending bosses at its central portion and a bore for a supporting rod extending through the block and bosses, an angular socket projecting at one side of the bore to receive a bolt head, said socket having an outer wall with a flat surface and a slot in said wall to receive the body of the bolt, and said block having at the opposite side of said bore a rectangular projection parallel with said wall, said projection having beveled surfaces parallel with said bore and having a bolt receiving bore, between said surfaces, and a clamping cap adapted to fit over said projection, said cap having an opening to receive a clamping bolt and a slot to receive the end of a fiat resistance coil and having sloping flanges adapted to cooperate with beveled surfaces on said projection to grip the resistor, and a bolt in the latter bore for securing the cap to said projection.

7. A terminal member for a resistance element composed of a flat metal ribbon, comprising a unitary casting including a central portion having a hole to fit over a mounting rod, a portion at one side of the central portion having a tapered end and whose axis extends at right angles to the'axis of the hole, a cap to fit over said tapered end and having a corresponding internal taper, a bolt passing through the cap and into the tapered portion to draw them together and a slot through the cap to receive one end of the ribbon.

8. A terminal member for a resistance element composed of a flat metal ribbon, comprising a unitary casting including a central portion having a hole to fit over a mounting rod, a portion at one side of the central portion having a tapered end and whose axis extends at right angles to the axis of the hole, a cap to fit over said tapered end and having a slot to receive one end of the ribbon, and means for forcing the cap on to said tapered end.

9. In a rheostat, a frame having parallel crossrods, coil-supporting members extending between and supported by said rods, each member comprising a metal bar having an insulating covering, a helical edgewound resistance coil mounted on each of said members and having its ends adjacent said rods, terminal blocks for the ends of each coil mounted on the cross-rods at the same side of the axis of the coil and insulated from said rods, each block having an opening through which one of said rods extends and having a projection at the coil side of the rod with a flat surface against which one end of the coil rests and means on each block for clamping the end of a coil against said flat surface.

JOSEPH F. FRESE. 

